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FRIEDRICH GEORG WINKLER, OFZSOHOPPAU, SAXONY, GERMANY, ASSIGNOR TOROBERT E. LESTER, OF NEWYORK, N. Y.

METHOD OF SIFTING GRANULAR MATERIAL.

SPECIFICATION forming part of Letters Patent No. 400,619, dated April 2,v1889.

No. 40,357, and October 22, 1886, No. 39,709.

Toa/ZZ whom t may concern:

Be it known that Iv, FRIEDRICH GEORG. WINKLER, a subject of the King ofSaxony, residing at Zschoppau, in the Kingdom of Saxony, Germany, have4invented new and useful Improvements in the Method of Sifting Flour orlother Granular Materials through Sieves of Hollow Cylindrical Form, (forwhich I have obtained Letters Patent from the Geryman Empire, No.38,576, dated April 2, 1886,

No. 39,709, dated October 22, 1886,v and No. 40,357, dated July 8,1886,) of which the following is a specification.

This invention relates to a method of sifting flour or other granularmaterial through a bolting-cloth forming the curved surface of a drum,which consists in progressively subjecting the meal or other substancedeposited upon the inner surface of the bolting-cloth to the action,alternately, of radially-outward jets or currents of air ofcomparatively small area in cross-section, but of considerable pressure,and radially-inward currents of air of larger area in cross-section, butof relatively lower pressure, whereby the finervparticles of thematerial present are by the cur-v rents of high pressure blown ou twardthrough the meshes of the bolting-cloth, and immediately afterward anycoarser particles which may have lodged against the inner surface 'ofthe bolting-cloth are driven radially inward therefrom by the inwardmovement of the currents of air of low pressure.

The described wave lmotions of air arepropagated progressively aroundthe entire circumference of the drum by means of internal rotating fans,the spaces between which are closed at the ends. In front of theadvancing side of each fan the air is compressed, and a portion of it,which is expelled from the area of compression in an outward direction,performs the function of blowing the finer particles of the materialoperated upon through the rmeshes of the cloth. To promote theperformance of this function, a concentric system of detlecting barsarranged lengthwise of the drum is interposed between the inner surfaceof the bolting-cloth and the path of motion ofthe fans, whereby theoutwardly-pressadjacent portion of `the boltingcloth, which is thuscleared of obstruction in time for the action of the next followingoutward current ol' air. The materials thus dislodged from the innersurface of the bolting-cloth are arrested in their'inward movement bythe dei'lecting-bars, and before they have time to l Application filedAugust 24, 1887. Serial N o. 247,765. (No model.) Patented in GermanyApril 2, 1886, No. 38,576, July 8, 1886,

make their way entirely through the spaces between the bars are caughtand again thrown outward by the outward current of air generated by thenext following fan-stroke.

The presence of longitudinal deectingbars prevents the establishment ofa circular current of air around the inside of the sieve orbolting-cloth, which would otherwise be established by the rotation ofthe fans, and which by carrying with it portions of .the material lyingagainst the surface of the boltin gcloth would create an obstacle toradial currents through the bolting-cloth in either dii rection. Thedetlecting-bars, therefore, are

useful in two respects: They prevent the ma-l terial operated upon fromacquiring a circular movement around the inner surface of the Asieve orboltiug-cloth, and they deiiect the outgoingcurrents of air radiallytoward the sieve or bolting-cloth, and thus cause-such currents to blowor press the material operated upon directly through the meshes of thesieve or bolting-cloth. l

The fans employed maybe almost infinitely varied in the forms of theircross-section; but in all cases they extend longitudinally entirelyacross the rotating structure, and either terminate at their ends,respectively, in the opposed faces of parallel disks affixed to thefan-shaft or they terminate in close proximity to the opposed faces ofsome other parallel walls, so that in any case the spaces between thefans are closed at the ends, and thus when a partial vacuum isestablished in the said spaces by the radially-outward ejectiontherefrom of the compressed air in front of the advancing fan-surfacesthe only path for the return of air to supply such vacuum will be aninward path at the periphery of the rotating structure in the rear ofthe advancing fan-surfaces. It will thus be seen that the rotatingfan-structure imparts to the air at its periphery a series of outwardand inward vibratory movements, and is thus a wave-generator propagatinga wave of air in a circular path.

Apparatus suitable for carrying out the described method of sifting inthe manufacture of fiour is represented in the accompanying drawings.This apparatus is here referred to for illustration merely, and themechanical features of novelty which it contains are made the subject ofanother application for a patent, serially numbered 291,549, filedNovember 22, 1888.

The drawings represent a flour-bolt, and

are as follows:

Figure 1 is a central longitudinal section exhibiting a portion of thefan in elevation and showing a pulley for rotating the cylindricalsieve. Fig. 2 is a transverse vertical section taken through the planeindicated by the dotted line 0c on Fig. 1. Fig. 3 is a longitudinalhorizontal section taken through the plane indicated by the line y y onFig. 2, but showing intermediate gearing for rotating the cylindricalsieve. Fig. 4 is an end elevation. Fig. 5 is a transverse verticalsection taken through the plane indicated by the line zz on Fig. 3.Figs. 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, and 17 are transversesections of various forms of rotating wave-generating fans.

The drawings represent a bolting-chest, A, to the opposite ends of whichare affixed the gear-frames a a. Within the bolting-chest is apreferably-rotating drum, the curved surface of which is principallycomposed of a sieve or bolting-eloth, B. Within the sievedrum is arotating cylindrically-arranged system of defiecting-bars, C. Vithin thecylindrically-arranged system of defiecting-bars is a rapidly-rotatingwave-generator consisting of fans D D, fastened at their opposite ends,respectively, to the two heads or disks D D', which are respectivelysecured to the flanges d d of a hollow shaft, d, keyed to therapidly-revolving shaft E. The shaft E is journaled at its oppositeends, respectively, in the boxes e e', carried in the hollow bosses a a,cast on the ends of' the gear-frames a a. The heads b b of' the sieveare provided, respectively, with the hollow hubs b b2, journaled in theboxes b3 b4, which derive their support `from the gear-frames,respectively. The system of defiecting-bars C is supported upon theperipheries of two parallel disks, C C2, which are provided,respectively, with the hollow hubs C3 C4. The hollow hubs C3 C4 extendthrough the hubs b b2 and are journaled in the boxes C5 C, carried uponthe gear-frames. The hollow hubs b b2 are of sufficiently large diameterto afford considerable clearance for the hollow hubs C3 C, which in turnare made of large enough diameter to afford ample clearance for theswiftrunning shaft E. 1t is not absolutely essential that the sieve-drumshould rotate; but it is desirable in order to secure the uniform wearof the bolting-cloth. The shaft E is provided at one end with the fastand loose pulleys E and E2 for engaging the belt which drives thewave-generator. The pulley C7, affixed to the hollow hub C4, drives therotating system of deflecting-bars, and a spur-wheel, C8, affixed to thehub C3, engages and drives a pinion, C, affixed to a counter-shaft, C10,provided upon its inner end with the spurwheel C, which engages the gearC12, affixed to the hub b of the sieve-drum, as shown in Figs. 3 and 4.

In practice the sieve-drum will be driven at the rate of from, say,twenty to thirty revolutions per minute, the system of deflecting barsat from one hundred to two hundred revolutions per minute, and thewave-generator at from five hundred to eight hundred ,revolutions perminute.

The meal or other material to be sifted is introduced into the feedchuteF, through which it falls into the interior of the hollow hub b2, fromwhich it is conveyed, by means of the spiral screw-blade f, affixed tothe hub C4, into the space between the head b of the sieve-drum and thedisk C2, down which it falls to the interior surface of theboltingcloth, A blade, C13, affixed to and extending spirally around theexterior surface of the system of the defiecting-bars, serves togradually move the meal longitudinally along the inner surface of thebolting-cloth. The flour sifts through the meshes of the bolting-clothand is carried by means of a screw-conveyer, G, to the flour-dischargechute G. The bran gradually moved along the interior surface of thebolting-cloth finally escapes through the openings B in the head b intothe bran-discharge chute H.

As the sifting operation is performed merely by the vibratory motions ofthe air induced by the wave-generator, the fiour is discharged throughthe fiour-chute G and the bran is discharged through the bran-chute Hwithout any accompanying outward currents of air. The total quantity ofair in the bolting-chest remains unchanged, and the flour and bran aredischarged therefrom simply by their own gravity.

The sifting effect will be best promoted by stretching the bolting-clothtightly, so that it will not participate in the vibratory movements ofthe air induced by the wave-generator. The wave-generator illustrated inFig. 2 generates two waves. The compressed air in front of the advancingfan-surfaces I and IOO IIO

J is Idriven outward, as'indicated by the longer arrows, fromcomparatively small portions of the periphery of the wave-generator, andair much greater than the pressure of the inward current. Byenlarging-the diameter of the wave-generator a larger number of fans maybeemployed, and thus a larger number of waves maybe simultaneouslygenerated. Or-

dinarily, however, it will be sufficient to employ a doublewave-generator-that is, a generator with two fans generating two wavessimultaneously, respectively, on opposite-sides of the generator.

Wave-generators, so far as regards the forms and positions o f theirfans, are suscep- -tible of almost infinite variation. Examples of a fewof the possible modifications are represented in cross-section in Figs.6 to 17,

.i both inclusive.` ,Each of the double wavegenerators consists of twoparallel disks affixed to a rotating shaft and united to each other bylongitudinal partitions which Vin some `cases are fiat, in otherscurved, and which in some cases extend from the shaft outward toward theperiphery, and in othercases are united alongy one or both of theirlongitudinal edges. tion of rotation isindicated by a longconcentrically-curved arrow, the areas of rarefaction are approximatelyindicated by net-works of shade-lines, and the approximate directions ofthe induced vibratory air-currents are indicated by the short arrows ineachfigure.

YIt will be seen that'in all the forms of wavegenerators shown there areestablished cells or spaces extendinglongitudinally across thelwaVe-generatonwhich cells are open only toward k,the periphery, andhenceA that in all r cases the partial vacua established in parts .V plitude as dstingushed from centrifugal fans such as heretofore known,which operate to produce a blast of air by constantly ej ecting fromthe periphery air which is drawn in at the ends of Y the Vrotatingstructure. It will hence be seen that the essential characteristic ofwhat is herein termed a wave-generator is that the longitudinal. spacesor Ycells with which it is provided, irrespective oftheir shape incross- In all these figures the direcsection, shall be open only towardthe periphery of the rotating structure.

- It is to be remarked that as a rule the amplitude of thevair-vibrations will increase or decrease accordingly as'the speed ofrota y:ion of the wave-generator is increased or decreased, and it isalso to be observed that in wave-generators in which the fans arecomposed simply of radial or nearly radial partitions, as illustrated inFigs. 6, 7, and 8, there will be a tendency of the air expelled from theforward side of the fan to turn immediately over the outer edge of thefan and inward into the space behind the advancing fan. This difficulty,however, can be overcome by increasing the speed Vof .rotation of thegenerator. It may also be overcome .by the employment of a' group offanblades in comparatively close proximity to each other, as illustratedin Figs. l() and ll, or by the employment of a concentricallycurvedshield having its forward edge connected with the outer edge of thefan-blade and having its rear edge connectedl with the outer edge of thenext adjoining partition, as illustrated in Fig. lll. By either of theseexpedients the area of rarefaction is removed so far to the rear of thearea of extreme condensationthat the current of compressed air isejected against the sieve without loss of pressure. To such an extent isthis the case that to produce outward currents of air of given pressurethe form of generator illustrated in Fig. l will require to be rotatedat from two and a half to three times the speed of the generatorillustrated in Fig. ll. f

In practice a wave-generator of twenty-two inches diameter having theform illustrated in Fig. 2 has been found to be peculiarly effectivewhen used in a scalper and rotated at from three hundred to sevenhundred revolutions per minute. It will be understood that in thescalper the flour of relatively high specific gravity is separated fromthe bran, which is of relatively low specific gravity.

When the wavegenerator illustrated in Fig. 2 is employed in machines forsifting iiour, it is rotated at a speed of from one thousand to fifteenhundred revolutions per min-- ute.

These examples are given merely for the purpose of practicalillustration. l

The principles governing the construction of wave-generators are thosewhich have been described. The principle to be observed in operatingthem consists in so regulating their speed of rotation that the outwardcurrent ejected through a comparatively small area of the sieve willhave j ust sufficient pressure to force the finer material through themeshes, so that at the same time t-he quantity of air required to supplythe place of that thusej ected will enter the generator through acomparatively large area of the sieve, and hence at such low pressure onthe exterior of this comparatively large area of the sieve thatV therewill IOO IIO

be no danger of causing the sifting material to adhere to and clog theexterior of this portion of the sieve. It Will thus be seen that thisinvention is not limited to any particular` arrangement of fans in aWave-generator, but is present in any cylindrical sieve in which thereis employed a Wave-generator having the essential characteristics ofconstruction and mode of operation herein described.

In the drawings the cylindrically-arranged system of defiecting-bars,which, for the sake of brevity, may be called the deliectinggrate, isrepresented as composed of angle bars or slats.

It is to be understood that the invention is not limited to the usc of adetlecting-grate composed of angle-bars such as shown, but is equallypresent iu a sifter in which there is employed a deiiecting-gratecomposed of bars Which are parallel or approximately parallel with theaxis of the rotating structure, irrespective of the shape of the bars incross-section. The presence ot these bars, as has been explained,prevents the establishment of circular currents of air immediatelywithin the cylindrical sieve and insures the deiiection of the currentsof air ejected by the rotating fans.

Instead of employing intermediate gearing, as illustrated in Figs. 3 and4, for transmitting motion to rotate the sieve from the shaft C4 ot' therotating defiecting-grate, the hollenv hub Z9 of lthe disk I) of therotating sieve may be provided with the pulley B2, and may thus bedriven by the belt independently of the r0- tating deiiecting-grate.

It will be seen that by throwing the belt olf of the pulley 2 the sievewill remain stationary, and it will also be seen that thededecting-grate may be rotated or not, according to whether the belt isapplied to the driving-pulley CT. Thus either or both thedcflectinggrate and the sieve may be rotated or not, as may be desired.

lVhat is claimed as the invention is- The herein-described method ofsiftin g iour or other granular material through a sieve or I)olting-cloth forming the curved Wall of a cylindrical drum, whichconsists in the subjection of all parts of such sieve or boltingcloth,and hence the subjection of all portionsl of the granular materialcontained within the sieve or bolting-cloth, successively to theinfluence alternately of a relatively-strong current of air movingtransversely outward through a prescribed area of the sieve and arelatively-weak current of air moving transversely inward through alarger area of the sieve.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

FRIEDRICH GEORG IVINKLER.

\Vitnesses:

H. R. BIGELoW, G. HTSMANN.

